1. Field of the Invention
The present invention relates to a name system in a communication network, and a naming method, and particularly relates to a technique for implementing naming in which security is ensured in an Internet environment and a personal network in which a user can access his own device or data.
2. Description of the Related Art
Rapid progress is being made in ubiquitous communication environments for melding real space with a network, whereby real-space information of an RF-ID or sensor is obtained by a network, household appliances having network connectivity are controlled via a network, and other effects are obtained.
The speed and capacity of both wired and wireless communication networks are also rapidly increasing, and flat rate services are being introduced that to not depend on communication time or communication charges. Through a combination of these services, it has become possible for users to easily remotely operate a home or office device and retrieve necessary information via a network from any location.
Although convenience to the user increases in such an environment, a high degree of knowledge may be required of the user due to the complexity of the system, and danger may occur at the same time in that the likelihood of unexpected access to one's device or information by third parties may increase due to setting errors, system failures, or the like.
There is therefore a need for a system that is designed so that security problems do not occur and setup is easy or unnecessary.
When an extremely large number of devices are connected to a network, there must be a means for one to discover/specify a service to use or a device to connect to. For example, when a user wishes to record a television program that is to be broadcast the same night, the user must perform a reservation operation in a home video deck. At this time, even if the video deck itself is connected to a network, indicating the video deck by a character string or a number string such as an IP address still makes it difficult for the user to discover and operate the video deck from the network.
This problem may be overcome from two directions. One is to give a name to each device that is easily recognized by the user and is separate from the address. Nonetheless, since packet transfer depends on the address during actual communication, there is always a need for the user to memorize the address list by keeping a list of correlations (bindings) between the addresses and names of the devices, and performing an appropriate conversion between names and addresses. This arrangement is referred to as naming.
Another method for overcoming the abovementioned problem is to register the “capability” (service) of each device in advance in a specific server. When a user issues a request to the service for a desired action, e.g., “record television program,” the server searches for a device that provides a service that matches the request, and responds with the information, whereby the user can access the appropriate device. This arrangement is referred to as service discovery.
Service discovery techniques are generally more complex than naming techniques, and it is therefore considered difficult to ensure scalability.
These two types of techniques are not exclusive, and convenience to the user can be even further improved by combining the use of these techniques. For example, among techniques proposed in the past, an Intentional Name system (INS) (see Non-patent Document 1) has characteristics of both the abovementioned techniques.
In an INS, naming elements of each device include the position of the device, the type of service, the access characteristics, and the like, and the naming elements form a tree structure, whereby a user can easily discover a desired service that exists nearby. However, since propagation/sharing of name space is performed on a hop-by-hop basis, scalability on the Internet level is difficult to ensure.
In the present Internet, the Domain Name System (DNS) (see Non-patent Document 2) is utilized as the de facto standard name system.
DNS has a hierarchical naming space, and a name is composed of a combination of a device name and a domain (system) name. In the name “www.nict.go.jp,” for example, the “www” is the device name, and the “nict.go.jp” portion is the domain name. The domain name portion has a hierarchized structure (in the aforementioned example, jp→go→nict), and the name servers of each system are structured so as to have the same hierarchical structure. Device names can thereby be managed independently within each system, and Internet-size scalability is acquired through distributed accommodation in a hierarchical structure even when the number of domains or devices increases.
It would be preferable for DNS to continue to be used in the next-generation network that is the subject of the present invention, but several functions needed in the next-generation network would then be impossible to provide.
First, movement of the user is assumed in the next-generation network. Particularly in devices existing on a PAN, connection points on the Internet (or an IP-based backbone network) continue to change while the Radio Access Network (RAN, e.g., Ethernet (registered trademark), wireless LAN 802.11g, W-CDMA (registered trademark), and other access schemes) frequently changes according to movement of the device. The new connection point then does not necessarily belong to the same domain. In DNS, since the name of the device depends on the connection point, this name cannot be considered to essentially follow the mobility of the device.
A drawback of applying DNS to the next-generation network is that the information of all the devices is basically disclosed. An advantage of DNS is that all devices can be accessed by a user using a simple name when the devices are connected to the network. However, a name registered in DNS can also be referenced by another user, and assigning a common name or an easily guessed name to a device may unnecessarily invite access by other users. This is not expected to be a problem insofar as access control is appropriately set, but it is preferred from a management perspective that information of devices meant for personal use not be displayed to others.
Patent Document 3 discloses a system and method as a related conventional technique to search for a device on a local area network.
This system includes an address server for associating IP addresses of devices on the network with a group name, and a discoverable device located on a first subnet of the network, wherein the discoverable device has an IP address, the IP address of the discoverable device being associated with the group name; and a discovering device, located on a second subnet of the network, for creating a list of known subnets and known devices on the network, querying a name server for a list of IP addresses associated with the group name, contacting each returned address of a discoverable device associated with the group name for the IP subnet information of the discoverable device, determining the subnet of the discoverable device, and adding the discoverable device and the subnet of the discoverable device to the list.
[Non-patent Document 1]: W. Adjie-Winoto, et al., “The design and implementation of an intentional name system,” Proc. Of ACM SOSP '99, pp. 186-201, December 1999.
[Non-patent Document 2]: P. Mockapetris, “Domain Names-Concepts and Facilities,” IETF RFC 1034, November 1987.
[Patent Document 3]: Japanese Laid-open Patent Application No. 2003-258832